Objects are routinely packaged within tubes of plastic film. In such operations, a tube may be formed of a plastic film, with the tube being closed by means of an electrostatic or other sealing operation along its length and the object being sealed within the plastic film by means of a pair of heat seals at either end of the plastic film tube. Depending upon whether a shrink film is employed, the completed package may or may not then be subjected to a shrink tunnel to firmly wrap the film around the object and complete the packaging operation.
When employing such a packaging operation, it is often desired to vertically position the heat seals at approximately the vertical center of the object. In some cases, however, due to the shape of the object being packaged, it is desired to provide a heat seal at a consistently controlled position, other than at the vertical center. The ultimate goal of this seal placement is to equalize the stresses throughout the film, preventing film breakage and producing a more reliable seal.
A problem in designing heat sealing apparatus is the necessity for providing a sealing mechanism which can be fully vertically adjusted within its predetermined range to accommodate objects of varying heights while maintaining a vertically controlled seal.